1. Field of the Invention
The present invention relates to a surface mount module used in mobile communications equipment, various sensors and the like.
2. Description of the Background Art
As electronic equipment becomes thinner and more compact, various electronic components mounted therein must be also made thinner and more compact. Consequently, conventional through-hole mount technology is commonly replaced with surface mount technology which permits such electronic components to be made both thinner and more compact.
In contrast, for electronic components used in automobiles, through-hole mount technology is still often used in a variety of types of modules that are adopted for use in-vehicle optical transport systems.
For example, the in-vehicle network standard known as Media Oriented Systems Transport (MOST), which has been adopted mainly in Europe, employs through-hole mount two-core bidirectional fiber-optic modules in which two plastic optical fiber (POF) cores are employed for data communications (e.g., see “MOST Gaiyō [MOST Overview],” Nikkei Electronics No. 741, pp. 108–122, Apr. 19, 1999).
FIG. 8 is a side cross-sectional view of a light-emitting side bidirectional fiber-optic module (optical mini-jack module) constituting a through-hole mount two-core bidirectional fiber-optic module. FIG. 9 is a side cross-sectional view of the light-receiving side bidirectional fiber-optic module (optical mini-jack module).
First, the constitution of the light-receiving side bidirectional fiber-optic module will be described. In FIG. 8, numeral 80 denotes a fiber-optic jack-type plug which is connected to an optical mini-jack module 60; 61 denotes a housing for the optical mini-jack module 60, having an opening 61a on its front surface into which the tip of the fiber-optic jack 80 is inserted and connected, the opening being connected at its rear end to a chamber 61b formed in the housing; and 62 denotes a light-emitting device disposed within the chamber 61b so that it faces the end surface of the fiber-optic jack 80.
Further, numeral 63 denotes a lead-frame of the light-emitting device 62; 64 denotes a light-emitting IC that converts an electrical signal representing logic levels into a signal used to drive the light-emitting device; 65 denotes an LED which is a light-emitting device that converts a modulated electrical signal into an optical signal, with the IC 64 and the LED 65 each being disposed on the lead-frame 63, and wired. Numeral 67 denotes an encapsulating resin that is transparent to visible light, and that is used to encapsulate as a unit the light-emitting IC 64 and LED 65. A portion of the surface of the encapsulating resin 67 facing the end surface of the fiber-optic jack 80 is recessed, and a convex lens 67a is also formed as a unit with the resin 67 upon the recessed surface. Each of the leads of the lead-frame 63 has one end that is provided in the interior of the housing 61, with another end 63a protruding from the outside wall of the lower surface of the housing 61 to be used as an input/output connector. Hereinbelow, an end of each of the leads of the lead-frame 63 provided within the housing 61 is referred to as an inner end, while the other end of the same lead that protrudes from the outside wall of the lower surface of the housing 61 is referred to as an outer end. Numeral 90 denotes a substrate to which the fiber-optic module is mounted. When the fiber-optic module is mounted, outer ends of the leads are inserted into holes in the substrate 90 and joined to the bottom side of the substrate using a solder 69.
There now follows a description of the constitution of the light-receiving side fiber-optic module shown in FIG. 9. The only difference in constitution from the light-emitting side is that the light-receiving side fiber-optic module has, in place of the light-emitting device 62, a light receptor 72 that comprises a photodiode (PDi), which converts an optical signal to an electrical signal, and an IC that amplifies the logic level of the electrical signal. The remainder of the constitution is identical to that on the light-emitting side, and identical constituent elements are denoted by corresponding names and numerals, and detailed description of such elements is therefore omitted.
The electrical signal input from the outer end 63a of the light-emitting device 62 is converted to light by the IC 64 and LED 65. The light emitted by the LED 65 passes through the encapsulating resin 67, is condensed by the convex lens 67a, enters the fiber-optic jack 80 and is sent to a communicating party via the optical fiber connected to the jack. On the other hand, an optical signal sent from the communicating party and arriving through the optical fiber enters the light receptor 72 from the fiber-optic jack 80, is condensed by the convex lens 67a, passes through the encapsulating resin 67, is input to the IC 74, converted to an electronic signal and output from the outer end 63a. 